Airplane wing flaps



July 21, 1964 DORNIER ETAL AIRPLANE WING FLAPS Filed NOV. 10, 1961INVENTORS. 5/1. w as DOE/V152 ATIOEWZK United States Patent 3,141,637ALANE WING FLAPS Silvius Dornier, Friedrichshafen, and Oslrar Schrenk,Friedrichshafen-Manzell, Germany, assignors to Dornier-Werire G.m.b.H.,Friedrichshafen, Germany, a German firm Filed Nov. 10, 1961, Ser. No.151,515 Claims priority, application Germany Nov. 12, 1960 1 Claim. (Cl.244-42) The invention relates to airplane wings having flaps at theirtrailing edges, and more particularly to means for increasing the effectof the wing flaps, i.e., the diversion of the propeller slip stream forproducing lift.

In the patent application of Silvius Dornier et al., Serial No. 130,785,filed August 11, 1961, now Patent No. 3,129,907, it is proposed toincrease the lifting effect of the propeller slip stream when the fiapor flaps on the trailing edge of the airplane wing is or are extended bymaking the underside of the flap or of the rearmost flap, in case thereare several flaps behind each other, deeply concave whereby the angle atwhich the upper surface is placed relative to the bottom surface at thetrailing edge of the flap becomes very small. It has been found thatthis configuration of the second flap of a two-flap system makes thissystem as effective as a system having three or more flaps arrangedbehind each other at the trailing edge of an airplane wing.

It is an object of the present invention to provide a structure or" anairplane wing flap which substantially increases the diversion of thepropeller slip stream without unduly increasing the weight of the flap.This object is obtained by making the underside of the fiap vaulted andby swingably connecting an auxiliary substantially plane or platelikeairfoil to the underside of the flap and within the vault or cavityformed thereby. The auxiliary airfoil, when protracted or extended,moves away from the trailing edge of the flap and enlarges the cavity atthe underside of the flap wherein the air is diverted, upon extension ofthe main fiap. The auxiliary airfoil is adjacent to the rear portion ofthe underside of the flap when the latter is in retracted position.

In a modification of the invention the auxiliary airfoil is swungforward and closes a substantial portion of the cavity at the undersideof the flap when the latter is in retracted position. The forward edgeof the airfoil abuts against the leading edge of the flap when inretracted position.

In a further modification of the invention the auxiliary airfoil isreplaced by the rear portion of the flap which rear portion is hinged tothe forward portion of the flap. During normal flight, when the flap isin retracted position, the rear portion of the flap is in line with theforward portion of the flap. When the flap is extended, the rear portionthereof is at an angle with respect to the forward portion and enlargesthe cavity formed in the underside of the forward portion of the flap.

The novel features which are considered characteristic of the inventionare set forth with particularity in the appended claims. The inventionitself, however, and additional objects and advantages thereof will bestbe understood from the following description of embodiments thereof whenread in connection with the accompanying drawing wherein:

FIG. 1 is a diagrammatic cross sectional illustration of an airplanewing flap structure according to the invention.

3,141,637 Patented July 21, 1964 "ice FIG. 2 is a diagrammaticillustration of a modification of the structure shown in FIG. 1.

FIG. 3 is a diagrammatic cross sectional illustration of a furthermodification of an airplane wing flap according to the invention.

FIG. 4 is a diagrammatic large scale illustration of an actuatingmechanism forming part of the structure shown in FIG. 3.

Referring more particularly to FIG. 1 of the drawing, numeral 1designates the rear portion of an airplane wing. A flap 2 is connectedto the wing 1 in the conventional manner, not shown. The underside ofthe flap 2, particularly the forward portion thereof, is vaulted andforms a cavity 3. Due to this configuration of the underside of the flapthe angle formed by the underside and the top side of the flap at thetrailing edge thereof is very Small. An auxiliary rigid platelikeairfoil 4 is placed in the cavity 3 and hinged at 5 to the underside ofthe flap 2. FIG. 1 shows the device in protracted or extended position.When the fiap is in retracted position the airfoil 4 is in the positionindicated by a dotted line 4' which is codirectional with the undersideof the flap. The airfoil is adjacent to the rear portion of theunderside of the flap whereas in the protracted position the airfoil isaway from the trailing edge of the flap 2. In the protracted positionthe airfoil 4 forms a considerable enlargement of the cavity in theunderside of the fiap- 2 and increases the diverting effect of the flapon the propeller slip stream.

Aside from the hinge 5 the airfoil 4 is connected to the flap 2 by atoggle joint including levers 101 and 102, lever 101 being pivotallyconnected at 103 to the flap 2 and lever 102 being pivotally connectedat 104 to the airfoil 4.

In the modification shown in FIG. 2 of the device according to FIG. 1the airfoil 4 is swung forward upon retraction of the flap 2, until theforward edge of the airfoil 4 contacts the leading edge of the flap 2and the airfoil 4 covers the cavity 3, preventing disturbing currents atthe underside of the flap during normal forward flight. When the flap 2is protracted the airfoil 4 is swung away from the leading edge of theflap toward the trailing edge thereof to the position indicated by adotted line 4' in FIG. 2. This movement is limited by a lever mechanismsimilar to that shown in FIG. 1.

In lieu of the provision of an auxiliary airfoil as shown in FIGS. 1 and2 the entire rear portion 105 of the flap 2 may be swingably connectedby means of a hinge 5' to the forward portion of the flap 2 as shown inFIG. 3. When the flap is in retracted position the rear portion 105 iscodirectional with the underside of the flap and forms a smoothcontinuation of the forward portion as shown in solid lines in FIG. 3.When the flap is protracted or extended the rear portion 105 is movedinto the position 105' shown in dotted lines in FIG. 3.

FIG. 4 shows a mechanism for swinging the rear portion 105 of the flap 2relative to the forward portion of the flap. This mechanism comprises apinion 106 mounted on the pin of the hinge 5. A rack 107 cooperates withthe pinion 106 for swinging the rear portion 105 into the desiredposition. The rack 107 may be hydraulically operated in a conventionalmanner. In lieu of a rack and pinion a worm gear may be provided. It isalso possible to effect the desired relative position of the forwardportion and of the rear portion of the flap 2 by lever mechanismssimilar to those shown in FIGS. 1 and 2.

3 We claim: by the concavely shaped underside of the flap upon re- In anairplane wing having at least one fiap at the traction of said flap.trailing edge, said flap having a trailing edge and a leading edge, andan underside having at least a forward por- References Cited in the fileOf this Patenl tion concavely shaped and forming a deep cavity, an 5UNITED STATES PATENTS auxiliary airfoil swingably connected to theunderside of the flap for swinging said auxiliary airfoil away from the2136845 Fenton 1938 leading edge and from the trailing edge of the flapand FOREIGN PATENTS forming an enlarged substantially concavely shapedsur- 727,432 France 29, 1932 face at the underside ofthe flap uponextension of the 10 846 421 France June 5 1939 flap, and for swingingsaid auxiliary airfoil to abut against 71627 4 Jan 1942 the leading edgeof the flap for closing the cavity formed

